Spotting after Depo?

So, I got my very first depo shot in September and hadn’t been using any other kinds of birth control before it. I was supposed to get it again on December 7th but I decided not to get it a second time because it kept messing with my hormones and making me gain crazy weight.

I’ve been spotting for about a week now? I don’t know if it’s normal to be spotting after the shot is supposed to be out of my system? I haven’t had sex in about 2 months and my spotting looks like implantation bleeding plus I’ve been peeing a lot and having constant headaches... I don’t think I’m pregnant and I’m too scared to check....

Help???😅